What is the name of the first step in the water-purifying process during which particles clump together?

Coagulation is the initial step in water purification where chemicals (like alum) are added to neutralize charges on suspended particles, causing them to clump together into larger particles called floc. This is necessary because the particles are too small to settle on their own. Sedimentation follows coagulation - it's where the heavy floc settles to the bottom. Aeration adds oxygen and distillation is a completely different process involving boiling and condensation.